Image transmission system



SePt- 22, 1.936 R D. BROWN, JR t 2,054,893

IMAGE TRANSMI S S ION SYSTEM Filed March 21,4 1951 5 Sheets-Sheet l sept, 22, 193e.

R. D. BROWN` JR IMAGE TRANSMISSI ON SYSTEM Filed March 21, 1951 y 5 Sheets-Sheet 3 l Patented Sept. 22, 1936 UNITED STATE IMAGE TRANSMISSION SYSTEM Reynolds D. Brown, Jr., Philadelphia, Pa., as-l signor to Philadelphia Storage Battery Con'l-v pany, Philadelphia, Pa., a corporation of Penn'- 4 Sylvania Application, March `.21, 1931seria1 N. 524,364

3 Claims.

if This inventionrelates to image transmission systems and has particular reference to those systems in which the picture orimage is vtransmittedfand received by transmitting small elements of the image in av predetermined. order to -make up the complete image and receiving the elements of the image in the same order to make up the complete received image.

"The invention has for its general object the provision of a method of transmitting and for receiving th-e small elements of the image which will give-results heretofore unattainable.

A further object is to providea method-of scanning an object or image whichy comprises scanning the object in a plurality of non-recurring paths during 'each complete scanning cycle, whereby the object is resolved into'a great number of small scanned areas or elements to bring out Idetail, and eliminate objectionable backgroundlines and flicker. f

A still further object is to provide a method of scanning an object or image which comprises scanning the entireimage in paths having a general Idirection-and thereafter successively scanning the entire image in paths having a different 'general direction'during'a single complete scanning cycle, whereby the image of the object is first generally outlined and then vbuilt up gradually to give a higher degree of definition and detail than has heretofore been obtainable.

A further and more specific object of the invention is to provide a device according to this method which will enable the transmission of images of Y objects or pictures in a manner to more clearly bring out details .thereof and to eliminate robjectionable background lines and flicker.V y

A more specific object of the invention is to provide a device utilizing a smaller scanning disc than 'has heretofore Ybeen practical and having the attending advantages thereof.L The device also makes use of round holes in theV disc, which has added advantages.

Other objects and advantages of my invention will be apparentffrom the following description in connection with the accompanying drawings, in which: l

Fig. 1 shows in elevation a scanning device operating according to the general method of vmy .invention withsome parts in section for a `clear -disclosure thereof; y

Fig. 2 illustrates the path traversed byA a scanning element ofthe idisc of the device of Fig. 1 .and shows the portions of the picture area scanned by the element; and f l (ci. irs- 6) Fig. 3 illustrates the paths across the picture area traversed by eachof the scanning elements during the first4 revolution VVof the vdisc of the device of Fig. 1 about its axis.

Referring to Fig. 1, there is shown lin section y .a base I and side wall 2 of a box-like structure which may support 'and enclose Vmy device. Mounted on base I by means of suitable bolts or theflike is a supporting member 3, upon which in turn is mounted by any suitable means va motor 4. Motor A is provided with a hollow shaft 5 for a purpose to be described later. vMounted on shaft y5 by means of asuitable set screw 6 is an arm 1. As shown, one end ofarm 1 has formedthereon a ringmember 8 whichts snugly over shaft 5 135; and-has a tappedhole. 9 therethrough to receive the threaded set screw 6. Shaft 5 is provided with adepr-ession Il] into which the` end of set screw 6 fits. It lwill be apparent that arm 1 is locked to shaft 5 and will rotate therewith. The opposite end of arm 1 has formed thereon a Asleeve yI I throughwhich ashaft I2 passes. The shaft I2 is rotatable within the sleeve and has mounted on one end, by means of a suitable flange I3 and screws I4, a-scanning disc I5. VThe ange I3 vmay be formed as an vintegral part of shaft I2. Shaft I2 is also provided with collars I6 mounted thereon-in any suitable mann-er, such as by means of set screws, to prevent the shaft from moving 'enclwise in sleeve II.- 30

The opposite end of shaft I2is of smaller diameter and has keyed thereto a pinion.I1 which rests against the shoulder of shaft I2. A Washer I8, /nut I9, and cotter key 20 provide means for locking the pinion. on the shaft. The frame. of motor 4 is formed so as to have an annular surface 2| with tapped holes v22 therein. VA collar member 23 fits snugly over surface 2I and is also provided with holesA which coincide with holes 22. Screws k24 pass through the holes of.r member 23 and threadedly engagel the tapped holes 22 to firmly secure collar 23 on the motor frame. Integral with collar23 is an annular frame 25 having gear teeth 2E formed about the periphery thereof to provide a xed gear, which meshes with pinion I1. I-Ioles 21 are provided in frame 25 to give jaccess to s-et screwG. From the description thus far, it `will be apparent that rotation of motor shaft 5 will revolve'arm 1, which will carry the axis of the disc I5 in a circular path. The fixed motor frame ygear will then cause pinion I1 to rotate, thus rotating the disc I5 about its axis. A The disc I5 comprises the usual scanning disc with spirallyv arranged apertures or lenses adapted to ordinarily. scan horizontal lines of; thepic'- ture area. Side wall 2 is provided with an opening 28, about which is fastened in any desired manner, such as by screws 29, a truncated conical member 30 of any suitable opaque material. The smaller opening of member 30 is positioned adjacent the scanning disc I 5, so that the spirally arranged scanning elements would, with rotation of the disc about its axis, scan the area of the opening in a series of slightly curved, approximately horizontal paths during each rotation of the disc. It will be understood, of course,rthat the picture or object to be scanned, inthe case of transmission, may be located adjacent the scanning aperture, or an image thereof projected on a screen, and that any lens system may be used if desired. Alternatively, the object or image may be scanned by the beam from a light behind the scanning disc and photocells may be positioned adjacent the object. In the case of reception, the image of the object may be formed onthe plate or anode of the lamp. i Y

A support member 3I is mounted on member 3 and is provided with a sleeve 32 at its upper end. A hollow shaft 33 ts snugly within the sleeve and is fastened thereto by means of a winged top set screw 34. Shaft 33 passes through the hollow motor shaft 5 and supports a lamp socket 35, which may be removably mounted on the shaft in any suitable manner. One way, as shown, is to form the socket with a collared end which fits over a small diameter end of shaft 33. A glow lamp Y3l, having suitably shaped electrodes 3,8 and. 39 to properlyilluminate the desired area, is supported by socket 35. It will be understood, of course, that in the case of transmission, a light sensitive cell could be used,v or a constant light may be projected. A conductor 40 passes through shaft 33 and is connected to a contact in socket 35, the socket and shaft 33, of course, acting as the other conductor.

In operation, it will be understood that there will be a scanning device at both the transmitting and receiving stations operating in synchronsm. At the transmitting station, if the usual system is used, light directed towardV the object or picture to be transmitted will pass through theY apertures of the disc to the object and Will be reflected to vvary the current throughy a Vlight sensitive cell. After being transmitted in any suitable fashion, the variations will be received at the receiving station and will serve to reproduce an image of the objector picture on the plateor anode of the lamp.

The xed gear and pinion of my device may, of course, be given any desired ratio. I prefer, however, a ratio of six to one so that the pinion rotates siX times while passing around the gear once. Since each rotation of the arm 1, irrespective of the xed gear, carries pinion I'I through an entire revolution with respect tothe motor frame, and since thearm and pinion are rotating in the Asame direction, the speed ratio between the pinion and arm is ve to one. In other words, when the 'armhas rotated once, the pinion has rotated ve times on the arm and six4 times on the Xed gear.

AAs shown in Fig. 2, while the motor axis makes a single revolution, each scanning element of disc I5 traverses an epitrochoidal path Ywhich includes six different but overlapping portions of the area being scanned. In this gure, Vthe disc I5 Vis shown in an original position and is indicated as havingsix apertures' 4I arranged in spiral. The shaded area represents lthe area to be scanned. 'Ijhe pinion I'I and gear26 are represented by broken circles. Now if we consider the path of any one of the apertures, such as the outermost one, the path will be as indicated by the broken circles and lines. A portion only of the epitrochoidal path is shown for simplicity, but all p0rtions thereof which traverse the area being scanned are as shown. It will be apparent then that during each cycle (revolution of the motor shaft), each aperture will Vscan six non-recurring, overlapping paths of the area.

s During each rotation of the disc about its axis, the apertures will scan the entire area in a series of curved paths, as indicated in Fig. 3. In this figure, the gear 25 and pinion I1 are again represented by broken circles, and the shaded area represents the area Vto be scanned. The small broken circlesY and the curved broken lines represent the apertures and their paths across the area during the initial rotation of the disc about its axis. During each of the subsequent rotations of the disc in the cycle, the apertures will scan similar series of non-recurring, overlapping paths but of different directions.

Thus the whole area of the object or picture is scanned at least six times during each revolution or cycle of my device. A speed of two and one-half revolutions per second (150 revolutions per minute) of the motor will give fifteen scannings per seco-nd.V The disc will then rotate twelve and one-half revolutions'per second (750 revolutions per minute). It will be apparent that with my device,'a low motor speed is utilized, whereas the devices of the prior art, require a motor speed of nine hundred revolutions per minute, of six times the motor speed of my device, to give the same number kof scannings per second. It will be understood, of course, that I have used a six aperture disc for illustration purposes only. A larger disc with a larger number ofY apertures could be used in practice.

It is to be noted that since the paths of the apertures overlap, as shown in Figs. 2 and 3, the overlapping portions will be scanned by more than one aperture, and each aperture will scan the overlapping portions more than once, during each cycle. In other words, instead of fifteen scannings per second, the area will be scanned more often because the overlapping portions cover practically the entire area. The effect of this is to give fine scanning which gives more detail, reduces flicker, and eliminates background lines.

It will also be noted that my device utilizes and is particularly adapted to a round scanning area. A smallscanning disc sufiices to scan the entire area. A higher degree of efficiency and perfection using round apertures is attained than has heretofore been possible.` I'he device is compact and free from local mechanical or electrical interference.

Another important advantage of my method of scanning is that electrical disturbances, such as noises and hum, if present, are not reproduced asv regular recurring distortions, which are very annoying. With the ordinary method, disturbance impulses produce spaced horizontal dis-V turbance'lines' or areas on the reproduced image. With the present method, however, the disturbances are reproduced as lines running in `different directions giving the effect of a uni- 'form background. Obviously, this is not annoying to the observer, as is the case where regular Vlines are produced.

The use of a small scanning disc having round holes 'has numerous advantages and constitutes an important feature of a device using a scanllarge scanning disc.

Vfound Svery successful practical. application .in

nlngdiscforlcarrylng out1the scanning method of l my invention. A .smalldisc occupies. less space than the largerdiscs which are'requisite inprior art devices.. Since the diameter ofv the discV isl the largest dimension inI such "devices, they require as'much space as is necessary to accommodate the disc. 'I'he disc of .my device may be verysmalhin fact, little larger than. the diameter of the motor frame. Asa result'of the smalle'amount of space required by such a small disc, the latter places no `limitation on the space required by the deviceas a whole. The Ventire assembly may .be housed in. a smallcasing to form a compactdevice. Such' a devicerequires little space and in .additionis more portable than the bulky device made necessary by the use of a Thesearev important con-V slderations to theaverage userand. would; therefore, bear. directly onA thecommerciability oi the device.

.Another important feature of a small disc is that it has less inertia. vFrom the .standpoint of safety to the user, this is very important.r fThe large scanningy disc .required in Adevices ofY the prior art act much .the same as the fly-wheel of an engine'due to their high inertia. .A large disc, revolving at a speed of .say nine .hundred revolu- ,tions lper :minute is obviously a menace tothe safetyfof' anyone who happens to be near it. If it should break or become loose due to mechanical defects, the damage which it.imight do is readily'apparent. On the other hand, comparatively little'damage wouldy be likely to occur if a small disc rotating at a'low speed wereto break or become loose.' s

A" still further and important feature of a small disc is the fact thatit can be made extremely thin. Naturally, the large and cumbersome discs which are` required by devices. of the prior art have a limiting thickness. must beat least thick enough so that it'will not collap'sewhile remainingY stationary. Obviously, if alarge disc ofthis kind were made of leaf-like thickness, it would' not have suflicient'strength to maintain itself'rigid whilev standing still. This niayy be `morel .readily visualized by considering adlsc'ofy large diameter made' of paper.l fIt is readily apparent that such a disc would' not maintainitsrigidity in a'stationary state. `On the other hand, the disc of my invention may be of such comparatively small diameter that it may be of leaf-likethickness and will Vstill be suili cientlyistrong tov maintainl its'rigiditywhile standing still. The advantages of -being able to utilize such athin disc are readily apparent. The most Yimportant of these is perhaps the savingin material. Another important advantage is that such adisc venables an observer to view, the `reproduced-image from different positions in front of' the disc, whereaswith athick disc the deep walls'of the apertures restrict the angle oi.' vision and limit the visible area of the image.i

-- The use of a disc having round holes: rather than square or other shapedholes'also'has"numerous attending advantages. VThe :most-importantof: these is perhaps the ease 'with which such a disc may be manufactured accurately. VIt is a simple matter to" punch or bore extremely small holes in a thinslreet of material. 1However, it isA quite d'ilcult to obtain small square or other 'shaped holes in a similar piece'oi material. The smally round holes may, be Yreadily punched or bored in the material' whereas'the squareholes must be obtained by'meansbf suitable dies.

Heretofore, discs using round holes 'have' notV Thatr is, the disc devices of the prior art. f In my device, however. round holes'ndfsu'ccessful application :and are utilizedv in. a manner .tocompletely scan inline degree the desired area.- f

Itis to be understood that the specific structure: `described is for thepurpose of illustration only.N Manifestly, manychanges withinthe scope of-.the invention areV possible.- Itis within the scopev of'myiinvention to impart .to the discany desired motion in` addition to its ordinary` revolution. The structurev shown could obviously be modiiied in details. For example, instead of havingthe motor shaft hollow, an auxiliary hollow shaft could be provided which would be ldriven bythe-motor and would have the rotatingarm mounted thereon.v In. this instance, the motor frame could be rotatable so as to enable syn chronizing the motors, or the ilxedxgear which would be mounted on an independent support, could be rotatable.

' The method of scanning a given area in non'- recurring paths during a complete c'yclemay be applied by suitable apparatus tothe cathode-'ray ly vertically in rows and then', if desired; in other directions all in a single scanning cycle. It is of utmost importance to note, thereforepthat my invention contemplate-sa method ofl scanning which maybe Ycarried Aout by numerous devices'.

The numerous possibilities'and 'advantagesof .my vmethod of 'scanning may be more'readily visualized by a study ofv Figs. 2 and 3 of the draw'- ings. Whilethese'gures are intended primarily to illustrate the operation of the device of Fig. 1', they show clearly the method of scanning which my invention in its broad sense contemplates. As illustrated in` these iigures,.the method 'contemplates'the scanning of the object or desired areaa plurality of times from different directionsduring a complete scanning cycle.v During Vthe initial portion of the scanning cycle, the area question is completely scanned in a series of substantially parallel paths from a certain direction. This gives a complete picture and theremainder cf the cycleis devoted to'building up detail and definition. In the device of Fig. 1, for example, the desired area is completely scanned six times from different directions. Obviously, if they device'were stopped after the area had been scanned once, or in other Words, at the end of one-sixth cycle,v a complete picture would be obtained, although, `it would probably be lacking in detail'. Each successive scanfof the area from diierentzdirections builds up or addsl to thede'- tail and definition of thev picture already obtained. It might be said, therefore, that'the method of my device contemplates-resolving the picture or desired area .intoi-niinitely small portions by scanningfrom different directions.

. -,The advantage of such a method of scanning Awhich involves resolving the picture area into small portions may be readily appreciated by considering a small portion of the area having, say, a black and whitearea.l If the picture area were vscanned once from one direction'only, as in the oase of the ordinary scanning disc arrangement, the'details of the black and white areas' of the portion; in." question' 'might not be Aproperly brought: out.'` I-lovvever,4 if' thev picture` area is scanned 'a number oftimes during each cycle from different directions, as in the case of my improved method, the details of the respective areas of the portion in question would necessarily be brought out and made definite by at least one and probably more of the scannings. Considering, for example,l a vertical strip Vor area of the picture, the ordinary method of scanning such area would result in the reproduction of an area having the generalV contour of tangentially disposed circles, because the scanning apertures merely"sweep transversely across adjacent portions of the area. If the scanning method of the'p'resent invention is used, however, the area is scanned by having the scanning apertures sweep over thearea in different directions during each scanning cycle. Since'during one scanning the area will be swept over longitudinally by one vor more of the scanning apertures, the image `reproduced will be of the same contour as the scanned area, having sharply defined edges. Furthermore; the multiple scanning will greatly increase'the definition .of the details. 1

Other advantages resulting from this method of scanning are numerous and mayy readily be appreciated. For example, in the transmission of still pictures, with the ordinary device of the prior art, the operator receiving the picture must receive a complete cycle before he can determine the details of the picture. If he is uncertain as to Whether or not he desires to receive the particular picture, he .rnust,y nevertheless, receive an entire cycle to nd out .whether or not he desires it. In the transmission of still picturesfutilizing the method of my invention, however, the initial fraction of a cycle will give a complete picture. If this picture does not have sufcierit detail so that the operator can intelligently understand it,.he can receive another fraction of the-cycle which builds up the details of the picture. Thus, each succeeding fraction of the cycle, during which the picture area is completelyv scanned, builds up or adds to the detail of the picture transmitted during the first fraction of the cycle.

In the case of a device using a scanning disc to carry out my improved method, it is conceivable that the disc might be imperfect or that a hole might become clogged by foreign material, the disc might be imperfect in that one of the apertures or scanning elements might, for example, be slightly out of place. If either of these contingencies occurred in devices of-the prior art, wherein the picture area is scanned only once froma single direction during each cycle, it is readily perceivable that a distorted or imperfect picture would result. If a hole in the disc were slightly out of place, .there would be an area of the picture which would not be transmitted at all and another area in which the details would overlap. If one of the holes become clogged, there would be an area of the picture which would not be transmitted.

, Consider now what would happen if either of these contingencies occurred in a device operating according to my scanning method. During the initial fraction of a cycle, when the picture area is Vcompletelyr scanned, there would be an areaV which would not be transmitted, but the succeeding scannings of the picture area fromdifferent directions during theY remainder of the cycle would cause the omitted area of vthe picture to be transmitted. Of course, in anyA such case, the picture received would not be as perfect as if such contingency hadA not occurred. However, in all probability, the defects in the' 'picture would not be noticeable. In .other words, the method 'of scanning, which my invention contemplates, might be said tospread the: error out over the entire picture, making 'it less apparent, much the same as the spreading ofY any material in a layer, rather than having it concentrated in a pile, serves to make it thinner and less apparent.

In the case of a device for using a cathode ray to scan the desired picture ror object, it is conceivable that the mechanismwhich controls the rayand causes it to move in a spiral might get out of adjustment. Usually, a pairY of condensers having their plates on opposite sides of the ray are used to control the movement thereof, as

is well known in the art. lVoltages are applied to the condenser` plates, ,setting up electrostatic fields which influence the ray in the desired manner. It is easily conceivable that the voltages applied to the condenser plates might not always be exactly Y equal. For example,. if they were unequal, instead of the cathode ray describing a true spiral path, it would describe a distorted spiral path which would take an elliptical form rather than a circular form. The result of this is clearly obvious; The picture would be distorted to the same degree that the controlling voltages are unequal. One receiving such a picture would have difliculty in intelligently discerning the details thereof, if the picture were not entirely unintelligible.

If the method of my. invention is applied to a cathodel ray device, the ray, in addition to generating successive 'spirals'would also Vbe moved to obtain successive scanning of the. entire picture area in non-recurring paths during each cycle. If the voltages applied to the condenser plates of the device were unequal, as assumed above, any one'scanning of the picture area during a fraction of the scanning cycle, would give a distorted picture in the same manneras the ordinary cathode ray device. .Howevelg the successive scannings of the complete picture area duringthe other fractions of the scanning cycle would tend to balance the distortion and spread' it out over the entire picture. A fair pictureY would at least be obtained and would be intelligible to the person receiving it. I

A still further advantage of the present method resides 4in Ythe fact that no limitations are placed uponthe dimensions or shape of the scanning area. In devices of the prior art, radial and circumferentialliniits of the area cause distortion.' The upper andlower boundary lines of the scanning' area are circumferential with respect to the disc axis, and the side margin lines are radial with respect to such axis. For this reason, the radial distance between the innermost and outermost apertures of the disc must be small compared to the radius in order to give a practical shape to the scanning area.-V Obviously, such limitation is not present in my device and the disc apertures may be located as close as is practical to the disc axis. Another important advantage of my method is that it enables the attainment of improved definition notwithstanding the limitations imposed von .such systems by broadcast authorities. The regulation vof such systems by the authorities may impose denite limits on theV number of lines or areas scanned per second, or on the number of disc apertures for a particular speed. Obvious- -ly',better definitionand detail maybe obtained within the prescribed limit or with a certain number of pulses per second Vwith my 'method than could be obtained with prior art methods under the same circumstances.

The above pointed out advantages of my method of scanning are only a few which serve to i1- lustrate the many advantages which are inherent in such a method. M`any others will undoubtedly occur to persons skilled in the art. Since, as heretofore pointed out, my invention comprises broadly a method of scanning rather than any particular scanning device or system, it is to be understood that the device illustrated in Fig. 1 is for the purpose of illustration and disclosure only. My invention contemplates and is intended to cover any device which may be utilized to carry out the desired method of scanning. I desire it to be understood, therefore, thatY my invention is not to be limited by this disclosure but only by the prior art as reiiected in the scope of the appended claims.

I claim:

1. In an image transmission system, a scanning disc having a plurality of spirally arranged scanning elements, means for moving the axis of said disc in a circular orbit which lies in a plane perpendicular to the axis of the disc, and means for simultaneously rotating said disc about its axis.

2. In an image transmission system, a scanning disc having spirally arranged scanning elements mounted on a shaft having a pinion, a motor having a rotatable shaft, means associated with said motor shaft for moving the axis of said first shaft in a circular orbit, and stationary means associated with said pinion for rotating said first shaft.

3. In an image transmission system. a scanning disc having spirally arranged scanning elements mounted on a shaft having a pinion, a motor having a rotatable shaft, an arm connecting said shafts whereby the axis of said first shaft is moved in an orbit, and a xed gear meshing with said pinion whereby said first shaft is r0- tated.

REYNOLDS D. BROWN, JR. 

